Introduction to Onsite The introduction to septic systems program - - PDF document

6/7/2012 1

Introduction to Onsite Wastewater Treatment Systems – Septic Systems

Ryan Gerlich

Extension Program Specialist Department of Biological & Agricultural Engineering Texas AgriLife Extension Service

Introduction

The introduction to septic systems program covers:

• Function of a septic system
• Evaluation of septic tank operation
• Determining if a septic tank should be

pumped.

• How to live with a septic system

Onsite Wastewater Treatment System

Onsite wastewater treatment systems?

• Rural and Exurban wastewater

infrastructure

• Water Quality Protection
• 25 - 40%, Wastewater

Infrastructure What is the system called?

• OWTS – Onsite

Wastewater Treatment System; Nationally

• OSSF – On-Site Sewage

Facility; Texas

• Septic System

Permitting Wastewater Treatment Systems in Texas

• Texas Commission on Environmental

Quality (TCEQ), Chapter 285, 5000 gallons per day or less

 Local Authorized Agent – Usually local Health

Department

 TCEQ Regional Office

• TCEQ, Chapter 217, Greater

than 5000 gallons per day.

Malfunctioning Onsite System

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Malfunction

• Malfunctioning OSSF – An on-site

sewage facility that is causing a nuisance

• r is not operating in compliance with the

285 OSSF regulations.

Nuisance

• sewage, human excreta, or other organic

waste discharged or exposed in a manner that makes it a potential instrument or medium in the transmission of disease to or between persons

• an overflow from a septic tank or similar

device, including surface discharge from or groundwater contamination by a component of an on-site sewage facility; or

• a blatant discharge from an OSSF.

Evolution of wastewater treatment goals

• From outdoor plumbing to water reuse
• We need to review the history to

understand the present

Outdoor plumbing: the pit privy

• Goal: designated place
• No carrier needed to

convey waste

• Waste applied directly to

the soil

• Public health concerns

addressed

• Management: relocate

Indoor plumbing

• Convenience
• Water carrier to

convey waste out of facility

• ‘Collection system’
• Public health and

pathogens

• Management:

keep pipe flowing

Disposal

• Goal: limit human

contact

• Keep wastewater below

ground

• Disposal options
• Public health

 “Disposing” of pathogens  Treatment?

• Environment:

groundwater contamination

• Management:

install, flush and forget

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Septic tank and soil treatment area

• Changing goal:

 Disposal: effluent goes away versus treatment  Dispersal: TREATMENT is essential to good systems

• Address both public health AND environmental concerns
• Management:

 Disposal: often none at all;  Dispersal: System management is critical

Groundwater

Well Aerobic soil

Goal: TREATMENT AND DISPERSAL

• Changes in goals means:

 Siting requirements  Technological advancements  Choice of components and systems  System O&M  Management program

Decentralized Approach

What is an Onsite Wastewater Treatment System?

1.

Wastewater Source

2.

Collection and Storage

3.

Pretreatment components

4.

Final Treatment and Dispersal components

Wastewater source

• Facility type

 Domestic  Commercial  Industrial

• User

 Owner/family  Employees

Collection

• Piping from facility

with cleanout

 Blackwater  Graywater

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Collection options

• Holding tanks
• Composting toilets
• Incinerating toilets

Pretreatment

• Septic tanks
• Aerobic treatment

units

• Media filters
• Constructed wetlands
• Disinfection

Final Treatment and Dispersal Components

 Trench and bed

distribution

 Evapotranspiration

beds

 Low pressure

distribution trench

 Drip field  Spray field

How do we make the wastewater system work?

• Evaluate the wastewater

source

• Evaluate site

 Wastewater treatment  Wastewater acceptance

• Choose a final treatment

and dispersal component

• Choose the appropriate

pretreatment system

• Operation and

Maintenance

Minimum required separation distances

Choices of distribution for various soil types

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What is a conventional septic system?

Conventional Septic Tank System What is a Septic Tank?

• Water tight containers

 Concrete  Plastic/ Fiberglass

• Gravity separation/

detention time

 Typically 2-3 days  Heavy sinks  Lighter floats

• Calm conditions
• Screen assisted
• Anaerobic digestion

RISERS INLET TEE OUTLET TEE W/ EFFLUENT SCREEN LIDS SLUDGE CLEAR LAYER SCUM

What is a Grease Tank?

• Baffles extend lower in the tank to help

retain grease and oil

• Typically not needed in most residential

systems

• Necessary for restaurants

Gravity Trench Biomat

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Wastewater distribution method

• Gravity

 Sequential  Parallel

• Manifolds
• Beds
• Pressure dosed

trench

• Pressure distribution

in the Field

Distribution media

• Rock
• Chambers
• Gravelless pipe
• Synthetic media

Gravity Distribution Gravel-less Pipe Distribution Leaching Chambers

Low-Pressure Distribution System

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Mound Distribution Field

Role of vegetative cover in treatment system

• A healthy cover crop is essential for the

system to function properly. Plants will:

 Take up nutrients  Take up water  Stabilize the soil

and prevent erosion

 Provide food and

habitat for beneficial soil organisms

What is an aerobic treatment unit?

Aerobic Treatment Unit System

Aerobic vs. Anaerobic Processes (???)

• Aerobic

 Aerobic bacteria require O2 to live and grow  Aerobic treatment processes require O2 to proceed  Common condition in soil treatment, media filters,

ATUs

• Anaerobic

 Anaerobic bacteria grow in absence of free oxygen,O2  Anaerobic treatment processes do not use oxygen, but

consumption of items, breaks oxygen bonds Ex. SO4, NO3

 Common condition in septic tanks, processing tanks,

and usually any saturated environment

Aerobic Treatment Unit System

• Trash Tank

 Small septic tank  1 day retention time  Physical separation  Anaerobic digestion

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Aerobic tank

• Aerobic Microbes

 Require Oxygen to live and grow  Consume waste and bacteria

• Configurations

Suspended growth: Attached growth:

Aerobic Treatment Unit System

• Air supply

 Compressor / Aerator  Diffusers  Oxygen transfer to wastewater  Mixing of food and organisms

• Clarifier

 Process were the microbes,

cell waste and biomass settle

• ut of the water.

Aerobic Treatment Unit System

• Disinfection

 Disinfection, not sterilization  Chlorinator

• NOT SWIMMING POOL TABLETS!

 UV light

• Distribution

 Pump tank  Spray field

Water Quality – Spray Field

• High potential for human

contact with water

• Secondary- Quality Effluent
• Remove 85-98% of solids

and organic matter

• Remove pathogens?
• Soil for Final Treatment
• This is NOT drinking water!!

No Playing in Sprinklers!! Spray Field

• Low angle spray head

 < 15 degrees

• Clear area around

spray head – 10 feet in the direction of spray from the head

• Vegetation growing

for water and nutrient removal

• Reseed dead

vegetation

Feeding the System

Conventional and Aerobic Systems

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SEWAGE COMPOSITION

• Water carrying

waste – Hydraulic Loading

• Organic Loading

 BOD

TSS

• Pathogens
• Nutrients

 Phosphorus

Nitrogen

• Chemicals

Fats, oils and grease

Constituent State at room temperature Comments Fats Solid Non-toxic to the system, origin – animals, will separate in water Oils Liquid Non-toxic to the system, origin – plants, trouble separating in water Grease Solid Residual material on appliances; solid material on pans/equipment; petroleum products; moisturizers; bath oils; tanning oils; toxic to the wastewater system Room temperature assumes 74 degrees F A degreaser will move all components through a system

In-Home Businesses/Hobbies

• Add stronger waste
• Add chemicals
• Increase flow
• Examples of Businesses:

 Home photography

developing lab

 Barber shops  Day care  Bakery  Dog grooming  Taxidermy  Artist

Prescription Drugs and Antibiotics

• Can kill microbes living

in system

 Won’t discriminate against

• rganisms living in the

system

• Additional treatment

components may be necessary

• Increase maintenance

Septic System Additives

• Not been proven to be

beneficial to system performance

• Not recommended
• Break up particles that

are settled at the bottom and make them suspended

• Potential solids loading to

downstream components

Kitchen

• 20% of daily flow
• Dishwasher
• Garbage Disposal

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Dishwasher

• Adds surges of

wastewater

 Hydraulically

• verload system

 Homeowner should

space out loads

• Organic load

 Clean/scrape

dishes

Garbage Disposal

• Increases scum by 20%
• System should be pumped 1-2 years sooner

than without a garbage disposal

• Increases Organic Loading

 Smaller particles will take longer to settle  Organic matter had not been digested,

so it will take longer to break down

 Potential for fats and oils

• More water is used to wash out sink

Laundry 20%

• Use should be spread
• ut
• Liquid soap is

recommended

 Use less  Remove risk of fillers

in powders

Bathroom Fixtures 60%

• Garden tubs

 Use large volumes of water  Add hydraulic surges  How often it is used?

• Multi-head showers
• No every-use shower

cleaner

Bath and body oils

• Increases Fats, Oils and Grease
• If usage is great, may need more maintenance

Bathroom

• Only urine, feces, soap, toilet

paper and limited amounts of cleaner should be going down drain

• No feminine products,

prophylactics, cigarette butts, etc

• No every-flush toilet bowl

sanitizers

Septic Safe?

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Toilet Paper

• Number of rolls used

per week

• Results in faster

sludge build up

• Treated toilet paper

(with lotions) prevents paper from settling

• Wet wipe disposal is

discouraged

Cleaning Products

• Cumulative effects on system performance
• Look at Labels!
• DANGER; Means the chemical will kill the

bacteria, and its use should be minimized

• r eliminated
• WARNING; Means limited use should

have a minimal impact on the system.

• CAUTION: Typically means the product

will have little effect.

Drain Cleaner

• Toxic drain cleaners

can impact ability to properly treat wastewater

• Affect bacteria activity

Operation & Maintenance of Septic Systems

Gases and Chemicals of Concern

• Hydrogen Sulfide
• Sulfuric Acid (converted from H2S)
• Chlorine Gas
• CO(X)’s

 Carbon Dioxide  Carbon Monoxide

• Methane

Common Biological Hazards around the Site

• Kids
• Dogs
• Cats
• Insects
• Snakes
• Vegetation

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Conditions at the tank

Odors?

Tank material Septic tank configurations Tank access

Access Location:

 Inlet  Outlet  Center

Current operating condition

Liquid level in respect to

• utlet (inches):

 At  Above  Below

In:_______

Above At Below

Septic tank pumping recommended?

• Should be

pumped when total solids reach 25-33% of tank capacity.

• If ‘A’ is less

than 3”

• If ‘B’ is less

than 12” If recommended, did it happen?

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SCUM LAYER CLEAR LAYER SLUDGE LAYER

Is It full?

• Measure solids in the tank
• 60” deep
• 6” of Scum
• 18” of Sludge

[18”+ 6”] ÷ 60” x 100 = 40 % Layers?

Septic tank pumping recommended? Baffles

• Inlet baffle in place
• Outlet baffle in place
• Compartment baffle in place

Baffles

• Concrete
• Plastic
• Fiberglass

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Baffles - tees

Effluent screens

Effluent screen cleaning

• Screen is washed off directly

into the septic tank

• This is being done at the inlet

end of the tank to protect against cleanings going directly

• ut the outlet
• Some units have protection

against outflow or an extra screen that that operates during cleaning.

Tank structural condition

• Watertight (no visual leaks)
• Rebar exposed
• Root intrusion
• Corrosion or spalling

present

• Cracks
• Flex

Vegetation

• Trees in

distribution field

• Excessive

vegetation

• Uneven

vegetation

• Poor vegetation

Why perform maintenance?

• Keep systems

functioning properly

• Maintain effluent

quality

• Early detection of

problems

• Public health
• Environmental

Protection

• System reliability
• User satisfaction

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Public health

• Wastewater can contain disease causing

Pathogens

 Bacteria  Viruses  Parasites  Protozoa

Hepatitis A Virus Ascaris lumbricoides (roundworm)

Environmental protection

Treat contaminants before they reach surface water

• r groundwater

 Nutrients

• Phosphorus
• Nitrogen

 Organic loading  Pathogens

• Fecal coliforms
• E-coli

EPA water quality programs

• Onsite wastewater

treatment systems

 Non-point source of

pollution

• Total Maximum Daily

Loads

• Coastal Zone

Management Program

System reliability

Performance of all system components must be functional to achieve full treatment

• Components require

maintenance

• Service/maintenance

should extend life of components

Thank you

Ryan Gerlich

Office # 979-458-4185 ragerlich@ag.tamu.edu http://ossf.tamu.edu/